Slow LAN Speed in LL

[Charybdis]

Hi all,

my local LAN is slow in Linux Lite.

My system:
CPU: Ryzen 7 on Gigabyte board, 3 Gb RAM, onbard LAN card is classical 1 Gb.
And
CPU: Intel I5 3 Ghz, same as above
And...
It shouldn't matter much as I meet this problem on a few machines of more or less this class.
The test has been run on the same computers, once with LL, once with Windows.

My problem:
The speed of transfers is slow.

From (any used here) computer to a Synology NAS (Jumbo packet 9Kb enabled) 1 Gb LAN speed


The numbers:

* LL (no tweak)
Speed up/down is ~25 Kb/s


* Windows 7/10 (Jumbo packet 9Kb enabled)
Speed up/down is ~60 Kb/s

* Windows 7/10 (NO Jumbo packet)
Speed up/down is ~35 Kb/s

The transfer of large file becomes very (too very) long under LL.

There is something to be done in the LL configuration, I think. 

Thank you for reading this.